Buggy code:
public class RuleMLDocumentParser { private Hashtable < String , String > skolemMap ; private Vector < DefiniteClause > clauses ; private Vector < String > variableNames ; private int anonid = 1 ; private RuleMLTagNames tagNames = null ; private Logger logger = Logger . getLogger ( "jdrew.oo.util.RuleMLParser" ) ; private Hashtable < Integer , Vector < Integer > > varClasses ; public RuleMLDocumentParser ( RuleMLFormat format , Vector < DefiniteClause > clauses ) { } public void parseRuleMLDocument ( Document doc ) throws ParseException { } private Element getRuleMLRootElement ( Element documentRoot ) throws ParseException { String rootName = documentRoot . getLocalName ( ) ; Element ruleMLRoot = null ; if ( rootName . equals ( tagNames . RULEML ) ) { Element assertElement = getFirstChildElement ( documentRoot , tagNames . ASSERT ) ; if ( assertElement == null ) { throw new ParseException ( "<Assert><seq2seq4repair_space>has<seq2seq4repair_space>to<seq2seq4repair_space>be<seq2seq4repair_space>the<seq2seq4repair_space>first<seq2seq4repair_space>child<seq2seq4repair_space>of<seq2seq4repair_space>the<seq2seq4repair_space><RuleML>." ) ; } documentRoot = assertElement ; rootName = assertElement . getLocalName ( ) ; } if ( rootName . equals ( tagNames . ASSERT ) ) { ruleMLRoot = documentRoot ; Element ruleBaseElement = getFirstChildElement ( documentRoot , tagNames . RULEBASE ) ; Element andElement = null ; if ( ruleBaseElement != null ) { ruleMLRoot = ruleBaseElement ; andElement = getFirstChildElement ( ruleBaseElement , tagNames . AND ) ; } else <START_BUG> if ( ( andElement = getFirstChildElement ( ruleBaseElement , tagNames . AND ) ) != null ) { <END_BUG> ruleMLRoot = andElement ; } } else if ( rootName . equals ( tagNames . QUERY ) ) { ruleMLRoot = documentRoot ; } if ( ruleMLRoot == null ) { throw new ParseException ( String . format ( "Undefined<seq2seq4repair_space>RuleML<seq2seq4repair_space>root<seq2seq4repair_space>element<seq2seq4repair_space>(%s)" , rootName ) ) ; } return ruleMLRoot ; } private void RemoveReifyElements ( Element element ) { } private Term parseAssert ( Element ass ) throws ParseException { } private Vector < DefiniteClause > parseNegFact ( Element neg ) throws ParseException { } private DefiniteClause parseFact ( Element atom ) throws ParseException { } private Vector < DefiniteClause > parseImplies ( Element implies ) throws ParseException { } private Term parseOid ( Element oid ) throws ParseException { } private Term parseInd ( Element ind ) throws ParseException { } private Term parseData ( Element data ) throws ParseException { } private String generateAnonymousIdentifier ( ) { } private Term parseVar ( Element var ) throws ParseException { } private Term parsePlex ( Element plex ) throws ParseException { } private Term parseExpression ( Element expr ) throws ParseException { } private Term parseAtom ( Element atom , boolean head , boolean neg ) throws ParseException { } private Term parseSlot ( Element slot ) throws ParseException { } private Term parseResl ( Element resl ) throws ParseException { } private Term parseRepo ( Element repo ) throws ParseException { } private Term parseNaf ( Element naf ) throws ParseException { } private Term parseSkolem ( Element sko ) throws ParseException { } private int internVariable ( String varName ) { } private void fixVarTypes ( Term complexTerm , Hashtable < Integer , Integer > types ) { } private Hashtable < Integer , Integer > buildTypeTable ( ) throws ParseException { } private Term parseDefaultElement ( Element el ) throws ParseException { } private Element skipRoleTag ( Element element ) { } private Vector < Term > parseDefaultElements ( Element element ) throws ParseException { } private Element getFirstChildElement ( Element element , String childName ) { } private int getFirstChildElementIndex ( Elements elements , int startIndex ) { } private int parseTypeAttribute ( Element element ) throws ParseException { } private Term parseSimpleElement ( Element element ) throws ParseException { } private void resetVariables ( ) { } No newline ; at end ; of file ; }

Fix:
if ( ( andElement = getFirstChildElement ( documentRoot , tagNames . AND ) ) != null ) {